docs: def heartbeat(self):
          """
          Add/update the node in Redis. Needs to be called regularly by the
          client.
          """
          pipeline = self.conn.pipeline()
          now = time.time()
          for replica in self.replicas:
              pipeline.zadd(self.key, '{start}:{name}'.format(
                  start=replica[0],
                  name=replica[1]
              ), now)
          ret = pipeline.execute()
  
          # Only notify the other nodes if we're not in the ring yet.
          if any(ret):
              self._notify()